Fingerprint sensing and matching is a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes.
A particularly advantageous approach to fingerprint sensing is disclosed in U.S. Pat. No. 5,953,441 to Setlak and assigned to the assignee of the present invention. The fingerprint sensor is an integrated circuit sensor that drives the user's finger with an electric field signal and senses the electric field with an array of electric field sensing pixels on the integrated circuit substrate.
A particularly advantageous approach to multi-biometric fingerprint sensing is disclosed in U.S. Pat. No. 7,361,919 to Setlak, which is assigned to the assignee of the present invention and is incorporated in its entirety by reference. The Setlak patent discloses a multi-biometric finger sensor sensing different biometric characteristics of a user's finger that have different matching selectivities.
U.S. Pat. No. 6,289,114 to Mainguet, and assigned to the present assignee, and the entire contents of which are herein incorporated by reference, discloses a fingerprint sensor that includes a finger sensing integrated circuit (IC). The finger sensing IC includes a layer of piezoelectric or pyroelectric material placed between upper and lower electrodes to provide electric signals representative of an image of the ridges and valleys of the fingerprint. A plurality of images are stitched together as the user's finger is swiped over a relatively small sensor.
As fingerprint sensors become increasingly popular, for example, for use in a portable electronic device, the amount of time spent by a user interacting with a fingerprint sensor increases. For example, a fingerprint sensor may be used to allow access to the portable electronic device, i.e. unlock the device, via a swipe of the user's finger when prompted by the device. The user's finger swipe generally has to meet certain criteria, for example, quality and speed, to be recognized by the fingerprint sensor. An improper or bad finger swipe, for example, that may not meet certain speed and quality criteria, may generate an error message and force the user to re-swipe her finger. This may become increasingly time consuming and frustrating for the user. More particularly, a user, with each improper swipe, may try another finger motion or speed, which may be unnatural and non-intuitive. Moreover, training a user on a proper swipe is also time consuming. Thus, as the use of a fingerprint sensor in a portable electronic device becomes increasingly popular, it may be desirable to include additional features.